Refrigerated goods are routinely shipped from manufacturers to distribution centers, and from distribution centers to retail outlets, in trucks, train cars and other transport vehicles. When loading and unloading refrigerated goods, refrigerated air easily escapes through the large doors of a refrigerated compartment, and warmer environmental air likewise enters. If the temperature of the goods exceeds a regulatory upper limit, and the frozen goods partially or completely thaw, the goods can be rendered unsellable and must be wasted. To avoid warming of refrigerated goods, a truck engine may need to remain running to power a continuously or repeatedly operating refrigerator unit, consuming fuel, raising the cost of shipping, and producing a large volume of exhaust even when the truck is not being driven.
Various devices are known and used in the shipping industry to control the amount of thermal variation in refrigerated compartments during loading and unloading operations. Bulkheads are relatively large and rigid structural members that can be disposed and arranged to span an opening to a refrigerated compartment, to limit an amount of airflow into or out of the compartment. Bulkheads can be composed of a thermally-insulating material such as expanded polystyrene foam or another material.
However, nearly all bulkheads share certain undesirable features. Firstly, bulkheads are large and unwieldy, making them difficult to constantly remove and replace each time goods are withdrawn from or placed into the refrigerated compartment. This same characteristic means that they consume a large amount of space when stored.
Secondly, the same relatively lightweight materials typically used to provide a bulkhead's thermal insulating properties and rigidity, are also substantially brittle and subject to damage due to repeated handling during use. Therefore, bulkheads must be replaced periodically, sometimes frequently, adding to their total cost of use and directing large units of relatively non-biodegrading materials to landfills.
Thirdly, because bulkheads are typically formed as individual structural units, and are not affixed to the structure of a compartment, bulkheads clutter a loading dock area when removed from a truck interior. During loading and unloading operations, the displaced bulkheads increase the risk of damage to the bulk heads, damage to products, and injury to workers, and affect productivity, as workers must attempt to avoid the bulkheads while carrying loads of products.
Another device used to control airflow into and out of a refrigerated shipping compartment is a curtain composed of sequentially overlapping, vertically-hanging plastic slats. Users can walk through the curtain by pushing adjacent slats outwardly from each other, and the slats then fall back into place once the person has passed through the curtain. Because of the large numbers of gaps between the slats, substantial quantities of air can pass through the curtain relatively unimpeded, particularly when air on one side of the curtain is pressurized or moving, as is common during loading and unloading due to a refrigerated unit and fan activating to maintain a temperature within the refrigerated compartment below a prescribed threshold for maintaining product quality. Additionally, in order to properly function, the individual slats typically do not contact a flooring surface, leaving a gap that colder air can readily transit through and escape from the refrigerated compartment.
Roll-down curtain devices that can be mounted within a refrigerated shipping compartment and rolled up and down during use are not unknown in the industry. However, the designs of current roll-down curtain devices induce one or more of several problems that complicate their installation or use, or limit their utility in one or more relevant ways.
First, most roll-down curtain devices are unitary, requiring that the entire unit be lifted into position and fastened to walls or a ceiling of a freight compartment of a truck, for example. The weight and bulk of such devices complicates the installation process, requiring two or more people; at least one to hold the device in position, and the other to attach fasteners between the device and the truck walls or ceiling. This process likewise increases the risk of stress-related injuries (e.g., twists, sprains, strains, etc.).
Secondly, many such devices include a spring-loaded latching device that locks the curtain in position due to a centrifugal action of the rotating curtain, and releases the curtain in response to contra-rotation of the curtain when pulled by a user, in the commonly-known manner of retraction and recovery of a window shade. Unfortunately, unlike a window shade, the weight of a curtain can cause spontaneous contra-rotation in response to bouncing and shaking of a truck during transit, allowing the curtain to unintentionally and uncontrollably retract, possibly damaging the curtain and defeating the purpose of deploying the curtain.
Thirdly, roll-down curtain devices that require some type of locking or latching feature between the deployed curtain and the floor of a refrigerated compartment—a hook for example—are subject to damage if struck with sufficient force by a person or a moving object, such as a forklift or shifting cargo. Once damaged, the curtain may no longer function properly, and must be repaired or replaced, which in turn can take the truck out of service for a period of time and affect productivity.
What is needed is a device that remedies some or all of the deficiencies discussed above and others observed in the prior art devices.